Use of an aqueous dispersion of at least one biodegradable polymer containing at least one stabilizing agent for the preparation of an aqueous filmogenic composition

ABSTRACT

The invention relates to the preparation of an aqueous filmogenic composition wherein dry matter, which is at least equal to 35%, for, is used in addition to an aqueous dispersion consisting of an organic phase dispersed in a dispersing aqueous phase, said dispersion containing, in relation to the dry matter, 94-99.5% dry organic phase comprising at least one biodegradable polymer, and 0.5-6% of at least one stabilizing agent.

The present invention relates to the use of an aqueous dispersion of at least one biodegradable polymer comprising at least one stabilizing agent, for the preparation of an aqueous film-forming composition with a high solids content.

The invention relates more particularly to the use of the film-forming composition thus obtained for the preparation of aqueous adhesive compositions and of aqueous pigment compositions.

Within the meaning of the present invention, the term “aqueous film-forming composition” is understood to mean a composition capable of forming a film or a coating by departure of the water initially present in said composition.

The term “aqueous adhesive composition” is understood to mean an aqueous film-forming composition capable of adhering to a support or of creating a seal between two other materials, whether identical or different in nature.

It can be in particular a composition for the temporary protection of metal sheets, a wood varnish, a composition for combating graffiti, a waterproofing composition for walls, a textile-finishing or -sizing composition, a composition for coating fertilizers, pharmaceuticals or seeds, or else an adhesive for leather, paper, wood, textiles (woven or nonwoven), synthetic fibers, plastics, glass and other materials.

Such aqueous adhesive compositions exhibit variable water contents generally of between 30 and 95% of the total weight of these compositions.

Water acts as inert dispersant or solvent for the constituents of these compositions and generally makes it possible to adjust the viscosity and the rheology of these compositions in order to allow them to be readily applied to the surface or material to be coated or sized, by coating, casting, spraying, dipping or immersing or by use of brushes, rollers, blocks or other instruments.

Such adhesive compositions essentially comprise binders and adjuvants, in the form dissolved in the water or simply dispersed in the water.

Within the meaning of the invention, the term “aqueous pigment composition” is also understood to mean a film-forming composition provided in the form of an aqueous suspension of pigments, binders and adjuvants.

The aqueous pigment compositions can in particular be coating colors, aqueous paints and aqueous film-forming pigment preparations, such as, for example, filler-comprising adhesives.

In paper-manufacturing applications, for example, such an aqueous pigment composition is the source of the finished appearance of the paper (opaque, white, smooth and glossy) and is responsible for its suitability for printing and in particular for color printing.

Water is an essential component of the pigment composition as it generally constitutes 30% and up to 95% of the total weight of said pigment compositions. It is the vector for all the other components.

Pigments constitute the solid filler of said aqueous pigment composition. They are generally substances of calcium carbonate, calcium sulfate, barium sulfate, calcium sulfoaluminate, kaolin, talc, titanium oxide or plastic pigment type.

In the case of the coating colors, the pigments generally constitute 80 to 92% by weight of the solids content (SC) of the aqueous pigment composition and generally have the role of covering the paper fibers or of conferring smoothness thereon, of contributing optical properties (whiteness, opacity, gloss) or of contributing printing properties (in the case of the coating color or of the coating film).

In the case of aqueous film-forming pigment preparations and paints, the amounts of pigments generally represent from 10 to 95% by weight of the solids content of the aqueous pigment composition and more generally from 35 to 95% by weight of the solids content, depending on the types of formulations selected (matt, satin or gloss paints).

The adjuvants for their part are auxiliary products present in the aqueous film-forming compositions, whether aqueous pigment compositions or aqueous adhesive compositions, in small amounts.

These introduced adjuvants indeed generally represent from 0.3 to 5%, even from 1 to 3%, by weight of the solids content of said aqueous film-forming composition.

They are generally classified into three categories.

The first category corresponds to formulating agents, such as alkaline agents, dispersing agents (sodium hexametaphosphate, sodium polyacrylate), wetting agents, antifoaming agents (mineral oils, silicone products, fatty acid esters, fatty amines) or biocides (quaternary ammonium, phenols, aldehydes, dyes).

The second category confers, on said film-forming composition, the ability to behave well on machines: it corresponds to rheology-modifying agents (such as cellulose compounds, polyurethane thickeners), water-retention aids (carboxymethylcellulose, starches and derivatives, caseins, proteins, polyols) or lubricants (calcium stearate, sulfonated oils, polyols).

This is because it is necessary for this aqueous film-forming composition to be able, in some cases, to be applied at high speed to the machines (rate that might be greater than 1500 m/min for paper machines).

The third category makes it possible to improve or to adjust the final characteristics of the aqueous film-forming composition: it can correspond to insolubilizing agents (crosslinking agents and resins, such as urea-formaldehyde, melamine-formaldehyde, glyoxal, zirconium salt), fluorescent whitening agents (di-, tetra- or hexasulfonated stilbene derivatives), coalescence agents or shading dyes (violet helio BNZ, unisperse blue).

The last constituent components of the aqueous film-forming composition, whether aqueous pigment composition or aqueous adhesive composition, are binders, which for their part generally represent:

-   -   from 5 to 20% of the solids content of the aqueous film-forming         composition in the case of the coating colors,     -   from 5 to 90% of the solids content of the aqueous film-forming         composition in the case of the aqueous film-forming pigment         preparations, such as filler-comprising adhesives,     -   and from 5 to 65% of the solids content of the aqueous         film-forming composition in the case of the paints, whether         matt, satin or gloss paints are involved.

They have in particular the role of ensuring the cohesion of the pigment layer or of the film or of the coating obtained subsequent to the departure of the water.

Their amount is selected with regard to the binding power of the adhesive used, the nature of the pigment(s) optionally incorporated and the concentration of the aqueous film-forming composition.

The binders employed are normally of natural origin, e.g. starch (wheat, corn) or protein (casein), or of synthetic origin, e.g. polyvinyl alcohol or latex.

More particularly, use is made of a latex (or “aqueous polymer dispersion”) which corresponds to a colloidal dispersion of synthetic polymers in an aqueous phase, i.e. a dispersion of microparticles of polymers in suspension in an aqueous phase, sometimes also referred to as polymer emulsion or suspension.

The conventional manufacture of an aqueous dispersion of synthetic polymers is based mainly on processes for the direct emulsion polymerization of synthetic monomers.

This type of latex generally comprises particles of polymers synthesized by direct emulsion polymerization of the pairs of monomers, for example, of styrene/butadiene, styrene/butyl acrylate, methyl methacrylate/butadiene or vinyl acetate/butyl acrylate type.

Each of these monomers confers, on the latex, properties of:

-   -   stiffness, gloss or absorption of inks (in the case of styrene,         acrylonitrile or methyl methacrylate),     -   resistance to solvents and oils (with acrylonitrile),     -   resistance to aging by UV radiation (with methyl methacrylate,         butyl acrylate or butadiene),     -   porosity (with vinyl acetate),     -   binding power or softness (with butyl acrylate or butadiene).

Generally, a synthetic latex thus employed in a film-forming composition exhibits a solids content of 45 to 60%, a density in the vicinity of 1, a Brookfield viscosity of 100 to 300 mPa·s and a pH of between 4.5 and 8.

However, it is known to a person skilled in the art that the major disadvantage of this type of aqueous dispersion of synthetic polymers, which limits the use thereof, is the fact that these synthetic products are not biodegradable or compostable and are furthermore difficult to recycle.

The absence of biodegradability presents serious environmental problems, in particular during treatment of waste by burying in the ground.

The proposal was then made to use starch derivatives as binders. However, while starch is biodegradable, it exhibits a poorer binding power and is sensitive to water, which is particularly harmful for the application of the film-forming composition, for example, in multicolor offset printing, where water is applied at each station, in wash-outs or in flexographic inks.

In order to overcome this problem, aqueous dispersions of polymers prepared from biodegradable polymers then formed the subject of intensive research and development.

The term “biodegradable polymer” is understood to mean a polymer capable of being decomposed under the action of microorganisms, in particular by soil microorganisms, but also under the action of natural agents, in particular water.

Such aqueous dispersions of biodegradable polymers are known but generally can only be obtained by the use of volatile organic solvents, such as, for example, disclosed in patent application JP 10-101911 and U.S. Pat. No. 5,747,584.

More particularly, U.S. Pat. No. 5,747,584 discloses in particular the use of aqueous dispersions of biodegradable polymers of PHA type to formulate adhesive dispersions which can be used for the adhesive bonding of nonwoven materials.

However, such aqueous dispersions are always prepared by use of toluene, ethyl acetate, acetone, halogenated solvents or other appropriate volatile organic solvents.

The term “volatile organic compound” is understood to mean any organic compound having a vapor pressure of 10 Pa or more at a temperature of 25° C. or having a corresponding volatility under given conditions.

To the knowledge of the Applicant Company, three types of process which make it possible to have available aqueous dispersions of at least one biodegradable polymer devoid of volatile organic solvents are, however, known to date.

The first type of process of the state of the art consist in the manufacture by extrusion of a dispersion of biodegradable polyester with a high solids content (SC) and with a very high viscosity.

Patent application EP 1 302 502 provides, in this sense, a process consisting in treating, at high temperature and at high pressure, by such an extrusion process, a melt blend of biodegradable polyesters with an aqueous emulsifier exhibiting a certain surface tension and with certain additives, so as to obtain an aqueous dispersion having an SC of at least 40% and a viscosity of at least 1000 mPa·s and preferably between 1500 and 10 000 mPa·s.

The process consists in melting the biodegradable polyesters in the extruder, and in then introducing therein the aqueous emulsifier downstream of the melt blend. The blend is subsequently kneaded at a temperature of less than or equal to 100° C.

Patent application WO 97/49762 also discloses an aqueous dispersion of biodegradable polymers capable of being obtained by extrusion, which comprises starches modified by esterification dispersed in an aqueous phase. This patent application also discloses a solvent-free process for the manufacture of said aqueous dispersions.

The process consists in preparing a melt blend, at a temperature of 100 to 180° C., of polymers and of optional plasticizers, and in then keeping this blend stirred at a high temperature, before gradually adding water and dispersing agents.

The second type of process of the state of the art which makes it possible to have available aqueous dispersions of at least one biodegradable polymer devoid of volatile organic solvents is that provided by the Applicant Company and consist in aqueous dispersions of at least one biodegradable polymer which are composed of an organic phase dispersed in a dispersing aqueous phase and which are devoid of volatile organic compounds, the dispersed organic phase of which comprises at least one viscosity-reducing agent.

These aqueous dispersions of at least one biodegradable polymer have formed the subject matter of a patent application, not yet examined, filed in France by the Applicant Company on 12 Sep. 2003.

These aqueous dispersions of at least one biodegradable polymer comprise a viscosity-reducing agent which exhibits specific characteristics in terms of solubility parameter and of ability to form hydrogen bonds and which is used in a specific weight ratio with said biodegradable polymer.

The viscosity-reducing agent (or “plasticizer”) is in this instance a heavy organic compound, preferably biodegradable or compostable, which, incorporated in the polymers, at least partially destroys the interactions between the chains responsible for the high viscosity and for the mechanical cohesion of said polymers.

Furthermore, the absence of volatile organic compound in these aqueous dispersions is reflected by a content of volatile organic compound (or VOC) which does not exceed that of the ingredients of said aqueous dispersions, i.e. at most equal to 5000 ppm, preferably of at most 1000 ppm and more preferably still of at most 500 ppm.

The third type of process of the state of the art makes it possible to directly obtain aqueous dispersions of at least one bacterial biodegradable polymer of polyhydroxyalkanoate type, of variable stability, from microorganisms comprising it.

This process can result in the preparation of aqueous dispersions of biodegradable polymers devoid of volatile organic solvents, since it is based on extraction by cell lysis, followed by purification by chemical or enzymatic routes of the native granules of biodegradable polymers.

A. Dufresne and E. Samain, in Macromolecules, 1998, 31, 6426-6433, describe the preparation of stable aqueous dispersions of poly(β-hydroxyoctanoate) or PHO from microbial strains of Pseudomonas oleovorans. Production is carried out by fermentation under controlled pH conditions and extraction of the aqueous PHO dispersion is carried out using sodium hypochlorite.

The spontaneous stability of these aqueous PHO dispersions is explained by the persistence around the polymer granules in suspension, of residues of a specific protein, in this instance the murein sacculus.

This type of process is also known for the preparation of aqueous dispersions of biodegradable polymers of microbial origin other than PHO, such as, for example, of hydroxyvalerate and hydroxybutyrate copolymers (PHBV).

The use of aqueous dispersions of biodegradable polymers devoid of volatile organic solvents, as binders in aqueous film-forming compositions, has in particular been developed in the state of the art with these aqueous dispersions of biodegradable polymers isolated from microbial strains.

Specifically, patent application WO 91/13207 discloses aqueous dispersions comprising a colloidal suspension in water of essentially amorphous particles of a polymer or copolymer formed of β-hydroxyalkanoates (for example, β-hydroxybutyrate and β-hydroxyvalerate), extracted in particular from the biomass of Alcaligenes eutrophus or Pseudomonas oleovorans, and its use in producing self-supporting films or biodegradable papers.

This patent discloses the possibility of having available latexes resulting from microorganisms which have the characteristics necessary for the use thereof as binders for pigment compositions and which exhibit the advantage of resulting in biodegradable and recyclable coating films or coated papers.

However, the binding properties of the latexes disclosed in this patent application are shown only by a single family of polyhydroxyalkanoates, the side chains of which comprise from 1 to 12 carbon atoms.

Furthermore, while these latexes exist in the native state in the form of essentially amorphous wet granules, they have the disadvantage of being arranged in a highly crystalline state, in particular once dried and/or after deposition on a substrate.

In point of fact, this aptitude for crystallization of these latexes does not destine them to be correctly employed in applications where it is essential, on the one hand, to promote the coalescence of the particles of the emulsion and, on the other hand, to obtain dry films exhibiting appropriate mechanical and optical properties.

Specifically, the ability of the aqueous polymer dispersions to form a film requires that perfect interpenetration/melting of the particles of the dispersed polymer be obtained after evaporation of the water (phenomenon referred to as “coalescence”).

For certain applications in coating colors, coating films or paints, it is thus essential to keep the latexes in the noncrystalline state in order to promote said melting of the particles at the surface of the substrate and to obtain mechanical and optical properties similar to those normally obtained with latexes of synthetic polymers which are nonbiodegradable or difficult to recycle.

It is therefore necessary, and it is this what is moreover recommended in patent application WO 91/13207, in order to prepare the pigment compositions, to improve the properties of this bacterial latex using surfactants of the soap or detergent type, in order precisely to limit the effects of the heat-induced crystallization of the latex.

For this reason, the pigment compositions disclosed in this international patent application, due to the ability of the biodegradable polymer to strongly crystallize after deposition on the substrate, do not appear to be suitable in practice for use in the fields of application targeted by the present invention of the Applicant Company.

Furthermore, in this international patent application, only the possible use of latexes exhibiting a solids content from 15 to 30% is envisaged for the formation of films, which is a particularly disadvantageous handicap in terms of speed of drying and of rate on industrial machines.

It is disclosed that, after evaporation of the water from the latex at ambient temperature, it is, however, possible to obtain a dense and transparent film with slightly improved mechanical properties by virtue of the use of halogenated solvents of chloroform type and/or by exposure to the vapors of these solvents during the drying of the film.

The necessary use of volatile organic solvents thus constitutes a second serious handicap to the industrial application of this process.

U.S. Pat. No. 6,024,784 discloses the use of poly(3-hydroxyalkanoate)s exhibiting mono- or polyunsaturated side chains of 6 to 16 carbon atoms extracted from Pseudomonas fluorescens, as binders in pigment compositions intended for the preparation of paints.

However, although the biodegradable polymers can be provided very generally in the form of latexes, U.S. Pat. No. 6,024,784 in reality envisages experimentally only the use of organic solutions of poly(3-hydroxyalkanoate)s (PHA) for the preparation of solvent paints.

Organic solvents of petroleum ether, diethyl ether or chloroform type, aromatic solvents of toluene or xylene type, or aliphatic solvents are recommended for dissolving the PHA, before it is used as binder.

This technical solution thus does not meet the environmental requirements desired as only solvent paint formulations are provided.

It results from all the above that there exists an unsatisfied need to provide a film-forming composition comprising an aqueous dispersion of at least one biodegradable polymer which is preferably devoid of any volatile organic compound, which has a high solids content, which can comprise only biodegradable ingredients and which is easily employed in the preparation of aqueous film-forming compositions, whether aqueous pigment compositions or aqueous adhesive compositions, such as coating colors, aqueous film-forming pigment preparations, adhesives or water paints, without it being necessary to carry out cumbersome, difficult and complex stages.

The Applicant Company has had the credit of reconciling all these objectives, hitherto supposed to be difficult to reconcile, by providing for the use of an aqueous dispersion of at least one biodegradable polymer comprising at least one stabilizing agent, present in a sufficient but not excessive amount, for the manufacture of such film-forming compositions.

The present invention thus relates to the use, for the preparation of an aqueous film-forming composition with a solids content at least equal to 30%, of an aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, said dispersion comprising, with respect to its solids content:

-   -   from 94 to 99.5% on a dry basis of organic phase comprising at         least one biodegradable polymer, and     -   from 0.5 to 6% of at least one stabilizing agent.

According to a specific embodiment of the invention, the dispersion used for the preparation of an aqueous film-forming composition with a solids content at least equal to 30% comprises, with respect to its solids content:

-   -   from 95 to 99.5% on a dry basis of organic phase comprising at         least one biodegradable polymer, and     -   from 0.5 to 5% of at least one stabilizing agent.

Preferably, the present invention relates to the use of an aqueous dispersion as defined above for the preparation of an aqueous film-forming composition exhibiting a solids content at least equal to 35% by weight on a dry basis, preferably of between 45 and 99.9% by weight on a dry basis, and more preferably still of between 50 and 75% by weight on a dry basis.

It is to the credit of the Applicant Company to propose the use of this aqueous dispersion exhibiting such a high level of biodegradable polymers for the preparation of aqueous film-forming compositions with a high solids content.

As was established above, the solids content, in the case of conventional aqueous pigment compositions, is provided mainly by the pigments, completed by the binders and to a lesser extent by the adjuvants.

The Applicant Company has thus overcome the technical prejudice according to which it becomes increasingly more difficult, indeed even impossible, to prepare a stable aqueous film-forming composition, whether aqueous pigment composition or aqueous adhesive composition, from an aqueous dispersion of at least one biodegradable polymer, as the dry matter content of said film-forming composition increases.

This is because the aqueous dispersions of at least one biodegradable polymer of the state of the art generally exhibit an excessively high viscosity.

For this reason, with a high solids content, in the case of aqueous pigment compositions, strong interactions between the pigments and the components of the aqueous dispersion are promoted.

The strong interactions can then bring about phase inversions, which result in the destruction of the homogeneity of the pigment composition while greatly increasing the viscosity.

This increase in viscosity becomes so great that it renders the pigment composition unsuitable for use in coating colors, in aqueous film-forming pigment preparations or in water paints.

In order to avoid this phenomenon of phase inversion, it is to the credit of the Applicant Company to have found that the presence of a stabilizing agent in the constituent aqueous dispersion of the film-forming composition was necessary in an appropriate amount which is sufficient but not excessive, in order not to harm good coalescence of the particles of dispersed organic phase.

These stabilizing agents can be proteins, starches, polyvinyl alcohols, gums, celluloses and polyols, in the native or modified form, taken alone or in combinations.

These stabilizing agents can also be polymeric emulsifiers, such as, for example, crosslinked acrylic copolymers of high molecular weight comprising a hydrophobic comonomer and in particular a crosslinked copolymer of acrylic acid and of alkyl methacrylates of 10 to 30 carbon atoms (such as Pemulen®, sold by Noveon).

The stabilizing agents are preferably polyvinyl alcohols with a degree of hydrolysis of between 60 and 98%, preferably of 70 to 90%, gum arabic, xanthan gum or modified starches or celluloses, preferably esterified (methylated, carboxymethylated, acetylated or alkyl succinylated) or etherified (cationic or hydroxypropylenated) starches or celluloses.

These stabilizing agents have to be present in the aqueous dispersion in a proportion of between 0.5 and 6% by dry weight, preferably of between 1 and 5.5% by dry weight, more preferably of between 0.5 and 5% and very preferably of between 1.5 and 5% by dry weight of the solids content of said aqueous dispersion.

It is then possible to incorporate from 94 to 99.5%, preferably from 95 to 99%, of biodegradable polymer(s) in said aqueous dispersion, which makes it possible to obtain an aqueous dispersion with a high level never yet achieved for the preparation of the aqueous film-forming composition in accordance with the invention.

This is because the Applicant Company has found that, at contents of stabilizing agents of less than 0.5%, the aqueous dispersion does not exhibit the stability sufficient to incorporate it as binder in an aqueous film-forming composition with a high solids content.

At contents of greater than 5%, the excessively high content of stabilizing agents is harmful to the coalescence properties necessary for the manufacture, for example, of coating colors, aqueous film-forming pigment preparations, water paints or aqueous adhesive compositions.

The aqueous film-forming composition in accordance with the invention is also characterized in that, both in its content and in its processing, it is preferably obtained by use of an aqueous dispersion devoid of volatile organic solvents.

The absence of volatile organic compounds in this aqueous film-forming composition is reflected by a VOC content which does not exceed that of the ingredients of said aqueous film-forming composition, i.e. at most equal to 15 000 ppm, preferably of at most 5000 ppm and more preferably still of at most 1000 ppm.

The aqueous film-forming composition in accordance with the invention thus does not exhibit any of the disadvantages of the preparations of the prior art and thus makes it possible to avoid the problems of toxicity, of additional costs, of complexity of the processing stages, with the necessity to install devices for preventing leaks, explosion-proof devices or devices for recovering the volatile organic solvents with their inevitable impact on the environment.

The Applicant Company has found that the choice of the type of aqueous dispersion devoid of volatile organic solvents is not a limiting factor, which is remarkable in itself.

Each of the known types of process for producing aqueous dispersions of at least one biodegradable polymer described above may thus be suitable.

This is because, by the choice of a given stabilizing agent, in given proportions, it is permitted to incorporate any type of biodegradable polymer in said aqueous dispersion.

The Applicant Company recommends only the use of aqueous dispersions comprising from 0.5 to 6% by weight of at least one stabilizing agent with respect to the dry weight of said aqueous dispersion for the preparation of aqueous film-forming compositions with a high solids content.

Advantageously, the Applicant Company recommends selecting more particularly two families of aqueous dispersions composed of an organic phase dispersed in a dispersing aqueous phase devoid of volatile organic compounds for the preparation of the aqueous film-forming composition with a high solids content in accordance with the invention.

The first family corresponds to the aqueous dispersions developed by the Applicant Company comprising, in their organic phase:

-   -   at least one viscosity-reducing agent exhibiting a solubility         parameter of between 15 and 28 (J.cm⁻³)^(0.5), preferably of         between 16 and 23 (J.cm⁻³)^(0.5), more preferably still of         between 18 and 21 (J.cm⁻³)^(0.5), and a hydrogen bond parameter         δH of between 3.5 and 15 (J.cm⁻³)^(0.5), preferably of between 4         and 13 (J.cm⁻³)^(0.5) and more preferably still of between 5 and         10 (J.cm⁻³)^(0.5), and     -   at least one biodegradable polymer in a weight ratio         polymer/viscosity-reducing agent of 99.8/0.2 to 60/40,         preferably of between 97/3 and 70/30, more preferably of between         92/8 and 70/30.

These aqueous dispersions exhibit a low viscosity even with a high solids content, so that they are particularly well suited to the preparation of pigment compositions with a high solids content in accordance with the invention.

The Applicant Company recommends selecting the viscosity-reducing agent from the group of the esters of acids and of alcohols which are optionally ethoxylated, preferably of the mono-, di- or triesters of organic acids, of carbonic acid and of phosphoric acid, of sugars or of polyols.

It can also be selected from the group of the ethers, optionally ethoxylated, of sugars, of polyols (in particular of isosorbide), of glycol or of phenol, of the ether esters of glycols or of the epoxidized triglyceride oils.

It is desirable to select one which is biodegradable or compostable and of food grade.

The viscosity-reducing agent also advantageously exhibits a boiling point of greater than 130° C., preferably of greater than 150° C. and more preferably still of greater than 200° C., which ranks it in the category of the heavy solvents particularly well suited to their function.

The Applicant Company recommends in particular selecting the viscosity-reducing agent from the group consisting of glycerol triacetate, isosorbide diacetate, isosorbide dibutylate, isosorbide diisobutylate, isosorbide dioctanoate, dimethyl isosorbide, ethyl lactate, butyl lactate, tributyl citrate, triethyl citrate, bis(2-ethylhexyl) adipate, diisobutyl adipate, dibutyl phthalate, propionic acid, glycerol tributyrate, glycerol triisobutyrate, ethylene glycol dibenzoate, diethylene glycol dibenzoate, propylene glycol dibenzoate, dipropylene glycol dibenzoate, triethylene glycol benzoate, dibutyl sebacate, diisobutyl sebacate, propylene carbonate, polyethylene glycol 400, polyethylene glycol 600, caprolactone diols with a molecular weight of approximately 500, vegetable oil methylesters and dibasic esters of adipic, succinic and/or glucaric acid.

For its part, the biodegradable polymer is noncrystallizable and is selected from the group consisting of biodegradable polymers of the following types: polylactates (or PLA), polymalates (or PMA), polyhydroxyalkanoates (or PHA), polycaprolactones (or PCL), polyesteramides (PEA), aliphatic copolyesters (PBSA) and aliphatic-co-terephthalate copolyesters (PBAT), and celluloses or starches which are highly acetylated or rendered hydrophobic by introduction of fixed fatty chains, taken alone or in combination, in the form of homopolymers or heteropolymers, whether linear, branched, crosslinked, dendritic or grafted.

Advantageously, the biodegradable polymers are heteropolymers, preferably di-, tri- or tetrapolymers, the monomers of which are diols, caprolactones or acids and hydroxy acids selected from the group consisting of D-lactic, L-lactic, glycolic, tetramethylglycolic, malic, β-propiolactic, butyric, valeric, phthalic, terephthalic, succinic, adipic, sebacic, hexanoic, octanoic, decanoic, dodecanoic, tetradecanoic, hexadecanoic and octadecanoic acids.

For the heteropolymers, the Applicant Company recommends selecting at least two monomers to be polymerized so that the first one is solid at ambient temperature and the second one is more fluid at this temperature. In this case, aqueous dispersions which are well suited to the formation of films are obtained.

The biodegradable polymers can be random, alternating, sequential or block heteropolymers.

The Applicant Company has shown that the ability of the polymers to strongly crystallize was not recommended for the aqueous dispersions intended for the preparation of aqueous film-forming compositions.

It is therefore advantageous to select a biodegradable polymer which is present in said dispersions in the noncrystallizable form, that is to say in the amorphous or in the semicrystalline form, and preferably in the amorphous form.

Moreover, the Applicant Company recommends maintaining said polymer in the amorphous or semicrystalline form after it has been applied to and/or dried on a support.

Within the meaning of the invention, the “amorphous” form of the biodegradable polymer comprises at most 25% of polymers in the crystalline form. The “semicrystalline” form comprises at most 60% of polymer in the crystalline form.

Optionally, a functionalized biodegradable polymer, preferably functionalized by a group of aldehyde, fluorinated, carboxylic acid, amine and alcohol type is selected.

Finally, the Applicant Company has found that the amorphous or semicrystalline biodegradable polymers of PHA type provided in particular by Procter & Gamble under the Nodax® trade name and the biodegradable polymers of PLA type provided in particular by Galactic under the Galastic® L68 trade name were particularly well suited.

Use may in particular be made of a blend of Nodax® with amorphous or semicrystalline PLA and/or starches which are highly acetylated or rendered completely hydrophobic.

The presence of a given stabilizing agent in specific proportions is necessary to prepare the aqueous dispersion suitable as binding agent of the aqueous film-forming composition in accordance with the invention.

This objective is easily achieved in this instance by the sequence of the following stages, which consist in:

1) preparing the organic phase to be dispersed of the aqueous dispersion by melting the blend of biodegradable polymer and of viscosity-reducing agent, at a temperature greater than the glass transition temperature of the biodegradable polymer, so as to obtain a homogeneous melt blend, the ratio of biodegradable polymer to viscosity-reducing agent being between 99.8/0.2 and 60/40, preferably between 97/3 and 70/30, more preferably between 92/8 and 70/30,

2) completely dissolving at least one stabilizing agent in the dispersing aqueous phase, so that it represents 0.5 to 6%, preferably 0.5 to 5%, by dry weight of the solids content of the aqueous dispersion,

3) simultaneously and continuously introducing the dispersing aqueous phase and the organic phase to be dispersed which are thus obtained into the mixer of an emulsifying unit, the flow rates for introduction of the two phases having been adjusted beforehand so that the dispersed organic phase represents at least 80% by weight of the solids content of said aqueous dispersions, preferably at least 90% by weight, more preferably still at least 95% by weight, and

4) recovering the aqueous dispersions thus obtained.

Use is made, for the preparation of said aqueous dispersions, of an emulsifying unit, for example an emulsifying unit such as one of those sold by Emulbitume (Trégueux—France) comprising:

-   -   a turbomixer,     -   two set-ups for preparing the organic phase to be dispersed and         the dispersing aqueous phase, each comprising a heat-insulated         vessel, a volumetric pump and an arrangement of heat-insulated         pipes.

This type of device makes possible the preparation of the aqueous dispersions at atmospheric pressure and at a flow rate of at least 100 l/h by simultaneously bringing into contact, in the mixer, on the one hand, the organic phase to be dispersed in the molten state, comprising the biodegradable polymer(s) with the viscosity-reducing agent, and, on the other hand, the dispersing aqueous phase, comprising the stabilizing agents.

The second family of aqueous dispersions composed of an organic phase dispersed in a dispersing aqueous phase devoid of volatile organic compounds which can be used for the preparation of aqueous film-forming compositions with a high solids content is directly extracted and purified from microorganisms.

The Applicant Company has found that, for the preparation of said aqueous film-forming composition in accordance with the invention, it is necessary to adjust the conditions for the purification of the native granules of biodegradable polymers so that their content of stabilizing agents, in particular of proteins, is between 1 and 5%, preferably between 1 and 4%, by dry weight with respect to the dry weight of the polymers.

This is because the Applicant Company has found that, at contents of stabilizing agents, in particular of proteins, of less than 1%, the aqueous dispersions of bacterial polymers did not generally exhibit a sufficient level of stability to be incorporated as binder of aqueous film-forming compositions with a high solids content.

At contents of greater than 5%, the excessively high content of stabilizing agents, in particular proteins, becomes harmful to the coalescence properties necessary for the manufacture of coating colors, aqueous film-forming pigment preparations, water paints or aqueous adhesive compositions.

The content of proteins in the native granules of bacterial polymers can be adjusted during the purification stages by any method known per se to a person skilled in the art.

The Applicant Company recommends using purification methods of the type of those employing sodium hypochlorite, which methods make it possible to digest the biomass without decomposing the polyhydroxyalkanoates and while leaving an amount of stabilizing proteins for the colloidal suspension sufficient to facilitate the coalescence of the native granules.

Preferably, the solids content of the aqueous dispersion used for the preparation of the aqueous film-forming compositions is between 25 and 70% by weight, preferably between 35 and 70% by weight and more preferably still between 45 and 65% by weight.

An aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, characterized in that it exhibits a solids content of between 25 and 70% by weight, preferably of between 35 and 70% by weight and more preferably still of between 45 and 65% by weight and, with respect to its solids content, from 95 to 99.5% on a dry basis of organic phase comprising at least one biodegradable polymer, and from 0.5 to 5% of at least one stabilizing agent, appears particularly suitable for the preparation of the aqueous film-forming composition in accordance with the invention.

For its part, the preparation of the aqueous film-forming composition in accordance with the invention is carried out by the blending of its constituents by any method known per se to a person skilled in the art, as will be exemplified below.

The aqueous film-forming composition thus obtained is particularly well suited to the manufacture of aqueous pigment compositions, such as coating colors, aqueous film-forming pigment preparations or paints, or also aqueous adhesive compositions.

Preferably, the aqueous pigment composition according to the invention exhibits a solids content at least equal to 30% and comprises:

-   -   as binder, an aqueous dispersion of biodegradable polymer         belonging to one of the families defined above,     -   at least one adjuvant,     -   and at least one pigment.

Preferably, the aqueous adhesive composition according to the invention exhibits a solids content at least equal to 30% and comprises:

-   -   as primary binder, an aqueous dispersion of biodegradable         polymer belonging to one of the families defined above,     -   as secondary binder, a polysaccharide selected in particular         from native and modified starches and native and modified         celluloses, which are preferably soluble in water,     -   at least one adjuvant,     -   and optionally at least one pigment.

The aqueous adhesive composition in accordance with the invention can in particular be an adhesive for labeling, for spiral mandrels, for corrugated board, for bag manufacture, for wallpaper, for carpets, including fitted carpets, for lining, for nonwoven materials, for cigarettes, wall.

It can also be a textile finish, a varnish, a composition for temporary protection, a composition for combating graffiti, a coating composition or a waterproofing composition.

The aqueous adhesive composition can be easily diluted with water depending on its method of application to the surface or the material to be coated or sized.

Other characteristics and advantages of the invention will become apparent on reading the nonlimiting examples described below.

EXAMPLE 1

Three aqueous pigment compositions with a high solids content are prepared from three aqueous dispersions devoid of volatile organic solvent.

A first aqueous dispersion (Dispersion No. 1) is prepared from the polylactate Galastic® L68, manufactured and sold by Galactic, exhibiting a number-average molecular weight of 68 000 Da, a polydispersity index of 2.78, a glass transition temperature of 55° C., a complex viscosity of 2380 Pa·s at 130° C. and of 34 Pa·s at 160° C., a degree of crystallinity of approximately 0% and a content of D-lactic acid after hydrolysis of 12.4%.

Use is made, as agent for reducing the viscosity of this polylactate, of diethylglycoldibenzoate, sold by Velsicol under the Benzoflex® 2-45 trade name, with a boiling point of 236° C.

For the aqueous phase, the stabilizing agent selected is the polyvinyl alcohol Poval JP 18Y, exhibiting a degree of hydrolysis of 88±1%, a viscosity of 25±2 mPa·s and a purity of greater than 94%, sold by TVP Japan Vam & Co. Ltd.

The process for the manufacture of the aqueous polylactate dispersion comprises the following stages:

1) Preparation of the Organic Phase to be Dispersed:

1300 g of pellets of PLA of Galastic® L68 type and 700 g of Benzoflex® 2-45 (i.e., a ratio of biodegradable polymer to viscosity-reducing agent of 65/35) are introduced into an electrically heated vessel maintained at 160° C.

When these products are completely molten, the blend is rendered homogeneous by stirring.

2) Preparation of the Dispersing Aqueous Phase:

135 g of polyvinyl alcohol Poval JP 18Y are dispersed in 3200 g of deionized water at 80° C. with mechanical stirring.

3) Preparation of the Aqueous Dispersion:

The simultaneous blending of the organic phase to be dispersed and of the dispersing aqueous phase is carried out in a laboratory emulsifying unit sold by Emulbitume.

The organic and aqueous phases are transferred into their respective heat-insulated vessels thermostatically controlled at 160° C. and 60° C.

The volumetric pumps are started up in a closed circuit in order to adjust the respective temperatures and to regulate the flow rates so as to obtain a content of dispersed organic phase of 97.2% and a content of stabilizing agent of 2.8%, with respect to the solids content of the aqueous dispersion.

After opening the valves, the organic and aqueous phases are conveyed simultaneously and continuously to the Atomix C turbomixer at 8900 rev/min.

A second, a third and a fourth aqueous polylactate dispersion are subsequently prepared according to the same procedure as above, except that:

-   -   for Dispersion No. 2, 85 g of Poval JP 18Y, 3.5 g of xanthan gum         (Sigma Aldrich) and 32 g of acetylated potato starch (A.N.=1.8)         extruded, manufactured and sold by the Applicant Company are         incorporated as stabilizing agents,     -   for Dispersion No. 3, 85 g of Poval JP 18Y, 7 g of xanthan gum         (Sigma Aldrich) and 64 g of acetylated potato starch (A.N.=1.8)         extruded, manufactured and sold by the Applicant Company are         incorporated as stabilizing agents, and     -   for Dispersion No. 4, 700 g of viscosity-reducing agent         Benzoflex® 2-45 are replaced by 325 g of diisobutyl adipate, 85         g of Poval JP 18Y, 7 g of xanthan gum (Sigma Aldrich) and 64 g         of acetylated potato starch (A.N.=1.8) extruded, manufactured         and sold by the Applicant Company are incorporated as         stabilizing agents and the pH is adjusted to a value of 5.0 by         addition of 1 N sodium hydroxide.

Tests are also carried out on producing two other dispersions by exactly repeating the conditions for the manufacture of Dispersion No. 1 but, for the first one, by adding only 18 g of Poval JP 18Y (i.e., a content of stabilizing agent on a dry basis/SC of 0.4%) and, for the second one, by adding 375 g of Poval JP 18Y (i.e., a content of stabilizing agent on a dry basis/SC of 7%). It is found that, in both cases, in contrast to the other 4 preparations, it is either impossible to obtain an aqueous dispersion or impossible to manufacture an aqueous dispersion exhibiting a stability of greater than a few hours (immediate coagulation).

The characteristics of the four stable aqueous dispersions are given in the following table I. TABLE I Disper- Disper- Disper- Disper- sion sion sion sion 1 2 3 4 Solids content (%) 59.7 59.5 57.5 46.1 Content of organic 97.2 97.5 96.4 94.6 phase on a dry basis/SC (%) Content of stabilizing 2.8 2.5 3.6 5.4 agents on a dry basis/ SC (%) pH 2.2 2.2 2.2 5.0 Mean diameter (μm) 5.1 5.0 5.4 4.2 Brookfield viscosity 390 495 870 3200 at 20° C. (mPa · s) Coagulation after absence absence absence absence 2 months

Three aqueous pigment compositions according to the invention are prepared, with Dispermat mechanical stirring at 5000 rev/min and for 2 min, by gradually adding 8 g of demineralized water and 35 g of one or other of Dispersions No. 1, 2 or 3 exhibiting the characteristics given in table I, to 16 g of an aqueous pigment suspension of calcium carbonate, sold by Omya under the Setacarb® brand, with a solids content of 75%.

These aqueous pigment compositions respectively obtained with Dispersions 1, 2 and 3 are referred to as PC1, PC2 and PC3. Their main characteristics are given in the following table II. TABLE II PC1 PC2 PC3 Solids content (%) 55.7 55.6 54.5 pH 6.4 6.6 6.5 Brookfield viscosity 2500 7200 4500 at 20° C. (mPa · s)

It is found that the aqueous pigment compositions thus obtained are stable in the sense that coagulation, flocculation or phase inversion are not observed. These pigment compositions furthermore exhibit good film-forming properties and a viscosity with a level that is acceptable for being used as aqueous film-forming pigment preparations.

Furthermore, starting from Dispersion No. 2, new aqueous dispersions (Dispersions No. 5 to No. 9) are prepared by adding, to this Dispersion No. 2, by simple mixing, as additional stabilizing agents, increasing amounts of a hydrogenated glucose syrup Polysorb® 70/12/12 as sold by the Applicant Company.

The amounts of this syrup, diluted to an SC of 59.5%, added to 100 g of Dispersion No. 2, itself with an SC of 59.5%, and the film-forming characteristics at 20° C. and at 95° C. of the Dispersions No. 5 to 9, are given in the following tables III and IV. TABLE III Dispersion No. 2 5 6 7 8 9 Polysorb 70/12/ 0 1 2 5 10 15 12 with an SC of 59.5% (g) Content of 2.5 3.5 4.5 7.5 12.5 17.5 stabilizing agents on a dry basis/SC (%) Content of organic 97.5 96.5 95.5 92.5 87.5 82.5 phase on a dry basis/SC (%)

TABLE IV Dispersion No. 2 5 6 7 8 9 Film-forming Very Good Good Poor Poor Very characteristics good poor (cohesion of the dry film) at 20° C. Film-forming Very Good Good Poor Poor Very characteristics good poor (cohesion of the dry film) at 95° C. (stoving) Resistance to Very Very Good Poor Poor Very water (films good good poor obtained at 95° C.) Visual Trans- Slight Slight Haze Haze Haze appearance parent haze haze 20° C. Visual Trans- Very Slight Haze Haze Haze appearance 95° C. parent slight haze haze Coalescence at Good Good Good Insuf- Insuf- Insuf- 20° C. ficient ficient ficient Coalescence at Good Good Good Insuf- Insuf- Insuf- 95° C. ficient ficient ficient

In fact, it is apparent that a content of stabilizing agents of between 0.5 and 5% on a dry basis of the SC of the aqueous dispersions makes it possible both:

-   -   to obtain stable aqueous dispersions (absence of coagulation or         of solidification, even after several months) additionally         exhibiting good film-forming properties and good properties of         resistance to water, and     -   to prepare pigment compositions also exhibiting good         film-forming properties while exhibiting Theological         characteristics suitable for their use as aqueous film-forming         pigment preparations.

EXAMPLE 2

An aqueous pigment composition intended for a coating color formulation of top coat/single coat type is prepared from Dispersion No. 4 of example 1 and is compared with a coating color formulation prepared from a synthetic aqueous dispersion in the following way:

1) Formulation of a “Top Coat/Single Coat” Coating Color from Dispersion No. 4 of Example 1 (Coating Color 1, According to the Invention)

The following are successively added with Rayneri mechanical stirring at 700 rev/min and for 1 hour:

-   -   1115 g of an aqueous pigment suspension of calcium carbonate,         sold by Omya under the Setacarb® 80 OG brand, with an SC of 76%,     -   328 g of an aqueous pigment suspension of kaolin, sold by Imerys         under the Supragloss® 95 brand, with an SC of 66%,     -   340 g of Dispersion No. 4,     -   126 g of plasticizer of polyol type manufactured and sold by the         Applicant Company under the Neosorb® 70/70 trade name, with an         SC of 70%,     -   12 g of dispersant, sold by Ciba under the Dispex® N40 brand,     -   61 g of thickener of carboxymethylcellulose type, sold by         Noviant under the Finnfix® 10 brand, with an SC of 10%,     -   10 g of insolubilizing agent, sold by BASF under the Urecoll® S         brand, with an SC of 56% and     -   8 g of lubricant, sold by Nopco Paper Technology under the         Nopcote® C 104 brand, with a solids content of 48%.

The solids content of the pigment composition is adjusted to 60% with demineralized water. The pH of this same pigment composition is adjusted to 9 with sodium hydroxide.

The viscosity, measured with a Brookfield viscometer, is 620 mPa·s at 100 rev/min and 30° C.

The viscosity, measured with a Hercules rheometer (model of DV-10 type manufactured by Kaltec Scientific Inc.) at a shear rate of 40 000 s⁻¹, is 42 mPa·s.

2) Formulation of a Control “Top Coat/Single Coat” Coating Color from a Synthetic Aqueous Dispersion (Coating Color 2):

The preparation of the control pigment composition is identical to that described above but Dispersion No. 4 is replaced by a synthetic aqueous dispersion of styrene-butadiene type sold by Dow under the Dow® DL 950 brand (solids content 50%; pH of 5.7; Brookfield viscosity of 98 mPa·s).

The solids content of the pigment composition is adjusted to 60% with demineralized water. The pH of this same pigment composition is adjusted to 9 with sodium hydroxide.

The viscosity, measured with a Brookfield viscometer, is 580 mPa·s at 100 rev/min and 30° C.

The viscosity, measured with a Hercules rheometer (model of DV-10 type manufactured by Kaltec Scientific Inc.) at a shear rate of 40 000 s⁻¹, is 24 mPa·s.

3) Coatings and Physical Measurements of the Coated Papers

These two pigment compositions are coated onto base paper with a grammage of 39 g/m² using a coating device of Helicoater® 2000 type manufactured and sold by Dixon. The coating carried out is of blade type (blade coating).

The amounts of these two pigment compositions deposited are respectively 19 g/m² for the composition comprising Dispersion No. 4 and 18 g/m² for the composition comprising the synthetic aqueous dispersion.

The papers are subsequently calendered using a laboratory calender of RK 22 HU type manufactured by Ramisch & Co.

The calendering step is a step necessary in order to confer a smooth and glossy appearance on the coated papers. The calendering conditions are 1 pass at 2.5 bar and at 120° C.

The papers, after having been stored in a climate-controlled chamber (23° C./50% RH), are subsequently analyzed, the results of which appear in the following table V: TABLE V Coating color 1 Coating color 2 (according to (according to the invention) the prior art) Whiteness (%) 82.3 81.4 Opacity (%) 92.1 90.7 Smoothness (ml/min) 25 26 Porosity (ml/min) 9 6 Machine direction 11 13 stiffness (mN)

The papers coated with the coating color in accordance with the invention, comprising Dispersion No. 4 (Coating color 1) give, in comparison with the coating color comprising the synthetic aqueous dispersion (Coating color 2), identical results in terms of smoothness, porosity and stiffness and better results in terms of whiteness and opacity.

EXAMPLE 3

The aqueous pigment composition PC1 as obtained according to example 1 is used as adhesive aqueous film-forming pigment preparation in comparison with a control adhesive formulation.

Said control adhesive formulation is prepared by blending, at 5000 rev/min for 2 min:

-   -   16 g of pigment suspension Setacarb® 85 OG, with a solids         content of 75%, sold by Omya,     -   8 g of demineralized water,     -   35 g of latex Rhodopass® A 013P, as sold by Rhodia (SC of 54%,         pH of 4.5, viscosity of 6000 mPa·s) and corresponding to a vinyl         acetate plasticized by dibutyl adipate. This control adhesive         formulation exhibits a Brookfield viscosity of 8500 mPa·s at 20°         C.

The adhesive bonding performances of the aqueous pigment composition PC1 of example 1 and the control formulation are evaluated comparatively according to a FIPAGO test in which the development of the adhesiveness is measured on a Strohlein apparatus.

The principle of this test consists in assessing the change over time in the tear strength developed by the adhesive compositions tested between two papers, one being placed on a stationery support and the other being attached to an articulated arm.

The two papers are of the same quality, have dimensions of 20 cm×6 cm and have the following main characteristics:

-   -   grammage: 66 g/m²     -   Cobb: 19 g/m²     -   AFNOR porosity: 7.6 ml/min     -   internal cohesion (Scott-Bond): 550 J/m²

The value 100 corresponds to the impossibility of separating the papers and the value 0 corresponds to immediate detachment.

For an amount deposited of 40 g of adhesive composition tested (PC1 or control preparation) per m² of paper, the results of FIPAGO adhesiveness presented in the following table VI are obtained: TABLE VI Adhesiveness after: 10 30 50 seconds seconds seconds Adhesive pigment 2 36 Defibering composition according of the paper to the invention Control adhesive 24 82 Defibering formulation of the paper

It is apparent that the adhesive pigment composition according to the invention, although resulting in slower adhesive bonding than the control adhesive formulation, exhibits good adhesive characteristics.

EXAMPLE 4

Two matt water paints and two satin water paints are prepared according to the compositions given in the following table VII, the styrene-acrylic binding resin Repolem® 2423 (latex with an SC of 50%, with a Brookfield viscosity of 10 000 mPa·s at 20° C., with a pH of approximately 8, with a minimum film-forming temperature of +15° C. and with a glass transition temperature of +18° C.) being completely replaced, weight for weight, by one or other of Dispersions No. 1 and No. 2 acting as binding resin. TABLE VII Composition in g Matt paints Satin paints Demineralized water 259.7 139.0 Cellulose thickener (Natrosol ® 3.7 1.0 Plus 430, Aquacon) Aqueous ammonia 0.1 0.1 (SC of 22%) Polyurethane thickener with 4.2 12.8 an SC of 50% (Coatex ® BR 100P, Coatex) Dispersant with an SC of 2.4 4.9 40% (Coatex ® P/90, Coatex) Antifoaming agent 0.4 1.5 (Nopco 8034 ®, Henkel) Biocide with an SC of 50% 1.7 2.0 (Acticide ® BX, Thor) White pigment (Titanium 77.8 222.6 dioxide R960, DuPont) Calcium carbonate pigment 84.8 40.5 (Durcal ® S, Omya) Calcium carbonate pigment 424.2 60.7 (Durcal ® 2, Omya) Binding resin 84.9 458.1 Demineralized water 50.9 55.9 Coalescent agent 4.3 0 (Texanol ®, Eastman) Antifoaming agent 0.9 0.9 (Nopco 8034 ®, Henkel) Aqueous ammonia q.s. for pH of q.s. for pH of (SC of 22%) approximately 8 approximately 8

The ingredients of the paints are incorporated in the order of presentation of table VII by following a fixed procedure and by using, for that, a disperser of Dispermat® CV brand especially designed for the preparation of paints.

The characteristics of the various matt or satin water paints are taken up in the following table VIII. TABLE VIII Matt paints Satin paints Repolem 2423 With With Repolem 2423 With With control Dispersion 1 Dispersion 2 control Dispersion 1 Dispersion 2 SC (%) 63.8  63.8  63.8  57.4  57.4  57.4  Brookfield viscosity (mPa · s) initial 9500    11 100    8400    19 000    13 000    8900    after 7 d 9700    15 000    12 500    18 000    15 000    13 000    pH initial 8.0 8.3 8.4 8.1 8.0 8.1 after 7 d 8.0 7.4 7.7 8.1 7.6 7.7 Presence of a yield No Yes Yes No Yes Yes point Measurement of 1   1   1   1   1   1   the flow (mm)* Sagging Absence Absence Absence Absence Absence Absence Appearance of the Smooth Smooth Less smooth Smooth Less smooth Less smooth film of paint after Matt Matt Matt Glossy Less glossy Rather matt drying Note: *= measured by the gap height in mm corresponding to the pair of streaks whose separation is still visible.

It is apparent that Dispersions No. 1 and No. 2 both make it possible to completely replace the nonbiodegradable synthetic binding resin Repolem® 2423 in the formulation of matt or satin water paints without compromising either their physical stability or their base properties.

It is advantageously apparent that the paints comprising Dispersions No. 1 and No. 2 exhibit, in contrast to the control paints, the yield point favorable to their application on a support.

EXAMPLE 5

An aqueous adhesive composition in accordance with the invention is prepared from an aqueous dispersion, devoid of organic solvents, of polylactate Galastic® L 68.

This aqueous dispersion is obtained according to the conditions described in example 1 (Dispersion No. 5) and comprises: demineralized water: 40.86% polyvinyl alcohol Poval JP 18Y: 1.07% xanthan gum: 0.07% polylactate Galastic ® L 68: 46.40% dipropylene glycol dibenzoate: 5.80% vegetable oil methyl ester: 5.80%

This dispersion exhibits a Brookfield viscosity of 650 mPa·s for a solids content of 56%.

The aqueous adhesive composition, which can be used as adhesive for cigarettes or adhesive for lining, is prepared by dispersing, in 700 g of demineralized water, 300 g of starch soluble in cold water sold by the Applicant Company under the trade name Dexylose® 250.

After stirring mechanically at 1500 rpm for 30 minutes, 300 g of the above aqueous dispersion are introduced.

The pH is subsequently adjusted to a value of 3 by addition of sodium hydroxide solution.

A homogeneous adhesive is thus obtained which exhibits a Brookfield viscosity of 4200 mPa·s for a solids content of 35.2%.

Adhesive bonding tests carried out on FIPAGO equipment show that this highly biodegradable and repulpable adhesive exhibits a very good ability to be used in paper lining, since defibering of the paper is recorded after only 30 seconds. 

1-13. (canceled)
 14. A method for forming a film, comprising the steps of a) preparing an aqueous film-forming composition with a solids content at least equal to 30%, wherein said aqueous film-forming composition comprises an aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, wherein said dispersion comprises, with respect to its solids content: from 94 to 99.5% on a dry basis of organic phase comprising at least one biodegradable polymer, and from 0.5 to 6% of at least one stabilizing agent; and b) applying said aqueous film-forming composition onto a support.
 15. The method as claimed in claim 14 wherein the film-forming composition exhibits a solids content at least equal to 35% by weight on a dry basis.
 16. The method as claimed in claim 14, wherein the film-forming composition exhibits a solids content of between 45 and 99.9% by weight on a dry basis.
 17. The method as claimed in claim 14, wherein the film-forming composition exhibits a solids content of between 50′ and 75% by weight on a dry basis.
 18. The method as claimed in claim 14 wherein the aqueous film-forming composition is an aqueous pigment composition or an aqueous adhesive composition.
 19. The method as claimed in claim 14, wherein the aqueous dispersion is devoid of volatile organic compounds.
 20. The method as claimed in claim 14, wherein the dispersed organic phase constituent of said aqueous dispersion comprises: at least one viscosity-reducing agent exhibiting a solubility parameter of between 15 and 28 (J.cm⁻³)^(0.5), and a hydrogen bond parameter δH of between 3.5 and 15 (J.cm⁻³)^(0.5) and at least one biodegradable polymer in a polymer/viscosity-reducing agent of weight ratio 99.8/0.2 to 60/40.
 21. The method as claimed in claim 14, wherein the dispersed organic phase constituent of said aqueous dispersion comprises: at least one viscosity-reducing agent exhibiting a solubility parameter of between 16 and 23 (J.cm⁻³)^(0.5), and a hydrogen bond parameter δH of between 4 and 13 (J.cm⁻³)^(0.5), and at least one biodegradable polymer in a polymer/viscosity-reducing agent of weight ratio of between 97/3 and 70/30.
 22. The method as claimed in claim 14, wherein the dispersed organic phase constituent of said aqueous dispersion comprises: at least one viscosity-reducing agent exhibiting a solubility parameter of between 18 and 21 (J.cm⁻³)^(0.5), and a hydrogen bond parameter δH of between 5 and 10 (J.cm⁻³)^(0.5), and at least one biodegradable polymer in a polymer/viscosity-reducing agent of weight ratio of between 92/8 and 70/30.
 23. The method as claimed in claim 14, wherein the aqueous dispersion is of bacterial origin and exhibits between 1 and 5%, of stabilizing agents.
 24. The method as claimed in claim 14, wherein the aqueous dispersion is of bacterial origin and exhibits between 1 and 4% of stabilizing agents.
 25. The method as claimed in claim 14, wherein the aqueous dispersion comprises a noncrystallizable biodegradable polymer.
 26. The method as claimed in claim 17, wherein the noncrystallizable biodegradable polymer is selected from the group consisting of biodegradable polymers of the following types: polylactates (or PLA), polymalates (or PMA), polyhydroxyalkanoates (or PHA), polycaprolactones (or PCL), polyesteramides (PEA), aliphatic copolyesters (PBSA) and aliphatic-co-terephthalate copolyesters (PBAT), and celluloses or starches which are highly acetylated or rendered hydrophobic by introduction of fixed fatty chains, taken alone or in combination, in the form of homopolymers or heteropolymers, whether linear, branched, crosslinked, dendritic or grafted.
 27. The method as claimed in claim 14, wherein the stabilizing agent is selected from the group consisting of proteins, starches, polyvinyl alcohols, gums, polymeric emulsifiers, celluloses and polyols, in their native or modified form, taken alone or in combination.
 28. The method as claimed in claim 14, wherein the aqueous film-forming composition thus obtained is intended for the preparation of pigment coating colors, aqueous film-forming pigment preparations and water paints.
 29. The method as claimed in claim 14, wherein the aqueous film-forming composition is intended for the preparation of aqueous adhesive compositions, in particular an adhesive for labeling, for spiral mandrels, for corrugated board, for bag manufacture, for wallpaper, for carpets, including fitted carpets, for lining, for nonwoven materials, for cigarettes, wall, a textile finish, a varnish, a composition for temporary protection, a composition for combating graffiti, a coating composition or a waterproofing composition.
 30. An aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, which exhibits: a solids content of between 25 and 70% by weight and, with respect to its solids content, from 95 to 99.5% on a dry basis of organic phase comprising at least one biodegradable polymer, and from 0.5 to 5% of at least one stabilizing agent.
 31. An aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, which exhibits: a solids content of between 35 and 70% by weight, and, with respect to its solids content, from 95 to 99.5% on a dry basis of organic phase comprising at least one biodegradable polymer, and from 0.5 to 5% of at least one stabilizing agent.
 32. An aqueous dispersion composed of an organic phase dispersed in a dispersing aqueous phase, which exhibits: a solids content of between 45 and 65% by weight, and, with respect to its solids content, from 95 to 99.5% on a dry basis of organic phase comprising at least one biodegradable polymer, and from 0.5 to 5% of at least one stabilizing agent.
 33. An aqueous pigment composition, which comprises an aqueous dispersion as claimed in claim
 30. 34. An aqueous adhesive composition, which comprises an aqueous dispersion as claimed in claims
 30. 35. An aqueous pigment composition, which comprises an aqueous dispersion as claimed in claim
 31. 36. An aqueous pigment composition, which comprises an aqueous dispersion as claimed in claim
 32. 37. An aqueous adhesive composition, which comprises an aqueous dispersion as claimed in claims
 31. 38. An aqueous adhesive composition, which comprises an aqueous dispersion as claimed in claims
 32. 